Cysteamine is approved in United States as a cystine-depleting agent for the treatment of cystinosis, a genetic disorder that causes an accumulation of the amino acid cystine in lysosomes. The compound has been proposed for use in treating non-alcoholic steatohepatitis, cystic fibrosis, Batten disease, Leigh syndrome, and Huntington's disease.
However, cysteamine exhibits poor oral absorption characteristics, having an absolute bioavailability of about 10% (Smolin et al., Ped Res. 1988; 23, 616-620). As a bitartrate salt for treating cystenosis, cysteamine is dosed up to 1.5 g every six hours; as a delayed-release formulation under the brand name Procysbi®, it is dosed twice a day. Furthermore, the drug requires an initial gradual dose titration over four to six weeks to minimize gastrointestinal side effects such as vomiting and abdominal pain.